Good for you, you have made it past the first winter. That is a significant milestone for new growers. Do you feel better now about having kept it cool for the winter?
No it is not too early for your tree to be outside mine all are as well. Junipers are pretty hardy so unless we (I'm near Pittsburgh) get a really bad cold snap I would not worry too much about it. A few hours at, or near, freezing will not harm it. If you are really concerned you can move it in at night if it is predicted to get really cold.1. Is it too early to move it outside if there is still a chance of the temp going below freezing?
Here is a link to the National Weather Service's forecast for your area, bookmark this link. I refer to it daily. If you scroll down and look to the right of the page you will see a link to an hourly weather graph that I find useful.
I may shelter some of my things tomorrow night, primarily things that have re-potted recently. I'll wait until Sunday afternoon and check the hourly forecast to make the decision.
I would not worry too much about that unless your tree is in a really heavily organic mix (we have not yet discussed growing mediums have we?) or you are getting steady rains for several days. I have my plants in a free draining mix so this is never an issue for me. The only plant I shelter from rain is my Chinese Elm that develops a fungus if the new, tender foliage is exposed to rain early in the spring.2. I know that it's very possible that it won't get enough water from rain, and that I need to check frequently if it's getting enough water. However, in this spring rainy season, is it possible for it to get TOO MUCH water? Is there anything I should do about that?
The location seems fine, outside with good sun and close enough to care for and enjoy. What is that structure it is on? That would seem to be a suitable location for shade lovers like Azaleas.
Norm
Learn how to pinch it and how to fertilize and re-pot as required. That way you will be better prepared when you seek your next tree.